Hysteresis effect of three-phase fluids in the high-intensity injection–production process of sandstone underground gas storages

Abstract

The unique high-intensity injection–production process of underground gas storages causes changes in reservoir and seepage parameters, which are crucial for safe and efficient operation. However, these parameters changes are frequently ignored in numerical simulations. In this study, two representative rock samples were selected for an experiment on relative permeability under the condition of high-speed injection and production. It was confirmed that multiphase fluid seepage in pores will produce hysteresis effect, which can limit the free exchange between different fluids in the process of injection and production. Based on the experiment results analysis, a mathematical model of the relative permeability hysteresis effect of three-phase fluid reservoir was established and applied to the numerical simulation of an underground gas storage. The influence of hysteresis effect on the numerical simulation process was evaluated, and the difference in the macro distribution law of oil, gas, and water in the stages of gas-reservoir development and underground gas storage injection-production was analysed. It shows that the relative permeability hysteresis effect must be activated in the injection–production process; otherwise, the actual seepage law of fluids and the range of transition zones cannot be accurately characterised; therefore, a high fitting accuracy cannot be achieved.